<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let c = 3 <= 5;
        console.log("c == ", c); // true

        // == 和 !=
        console.log("true == 1：", true == 1); // true
        console.log("false == 0：", false == 0); // true

        console.log("'true' == true：", "true" == true); // false
        console.log("true == '1'",true == '1'); // true
        console.log("1 == '1'",1 == '1'); // true

        console.log("undefined == null",undefined == null); // true
        console.log("null == 0",null == 0); // false

        console.log("+0 == -0", +0 == -0); // true

        // === 和 !== 先比较数据类型，再比较值
        console.log("true === 1：", true === 1); // false
        console.log("undefined === null：", undefined === null); // false
        console.log("+0 === -0", +0 === -0); // true
    </script>
</body>
</html>